Conventionally, a general purpose engine is configured that a flywheel and the like connected to a crankshaft of the engine is provided with a permanent magnet only at a single location in the circumferential direction, and a magnet generator is provided opposite the permanent magnet. The magnet generator includes an ignition coil having a primary coil wound over an outer peripheral side of a core, and a secondary coil is further wound on an outer peripheral side of the primary coil. The primary current is applied to the ignition coil at a voltage induced in the primary coil. The primary current is then cut off to obtain high voltage for ignition purpose.
Patent Literature 1 discloses an example of the ignition device used for the conventional general purpose engine. The disclosed ignition device for engine has a capacitor disposed at a primary side of the ignition coil so that the charging circuit charges the capacitor at the forward induced voltage in the primary coil of the ignition coil. A plurality of switches are provided for the discharging circuit of the capacitor. Those switches are sequentially turned on at the position having the phase advanced from the engine ignition position. At the ignition position, those switches are turned off.
Patent Literatures 2 to 4 disclose other examples of the generally employed engine ignition device. Patent Literature 2 discloses the ignition device intended to have a simplified and compact structure by eliminating the pulser coil. Such structure is established by allowing the main part of the voltage generated in the primary winding to be applied for ignition energy, and the sub part of the voltage to be applied for the power source and the rotation pulse generation source. The microcomputer controls the ignition timing by the signal transmission means with different polarity. Patent Literatures 3 and 4 disclose the ignition device which secures the minimum output at the ignition timing by detecting the proportional voltage of the trigger coil.